Snap vs. kickr6 resistance calculation

Hi everybody.
I just recently switched from a snap to kickr and was prepared for a reality check. And what a check that was, despite doing regular spindowns, having the tire pressure right etc. So I started to think, why this power drop happened and why it is so different for different riders. I did some research and noticed that the power drop is more with increased riders weight. So I was wondering, if the reason is just, that the snap does compute the applied resistance for a fixed riders weight of 75kg while the kickr takes the weight transmitted by the app (Zwift etc.). I think I read this somewhere. I know that at least Zwift does transmit the weight to the trainer since 2021, but what does the trainer with this info? Does anybody knows more about this?
Thanks for your insights!